Germany had lost territories, and my understanding is that those territories were still inhabited by Germans.
 

"(US president) Wilson proclaimed self-determination as a great principle—and then gave away chunks of German-speaking Europe to Czechoslovakia, Poland, Italy and France, sowing the seeds of the next war.
Knowing that Austria favored a union with Germany after Vienna lost its empire, Wilson wrote into the Treaty of Versailles an article barring the union, no matter how the Austrians voted.[...]"
 

Lloyd George, the British Prime Minister, during the Paris negotiations:
“I tell you once more, we would never have thought of giving to Poland a province that had not been Polish for the last 900 years…
The proposal of the Polish Commission that we should place 2,100,000 Germans under the control of a people which is of a different religion and which has never proved its capacity for stable self-government throughout its history, must, in my judgment, lead sooner or later to a new war in the East of Europe...” 11)

“France is not so much concerned with what is important to Poland, rather the French position is determined solely by the aim of weakening Germany.”12)

“To surround Germany with small states, many of which are composed of peoples that have never governed themselves and that comprise large numbers of Germans who are demanding reunion with their homeland, such plans would be, it seems to me, a breeding ground for the most terrible reason for a future war.” 13)
“I was as sincere an advocate of Polish independence as any member of the Commission, but I was convinced that to add to Poland populations which would be an alien and hostile element inside its boundaries would be a source of permanent weakness and danger and not of strength to this resurrected State.
I knew that a time would come when Germany would respond to the cry of its exiled people and restore them to the Fatherland by force of arms.
For that reason I renewed my pressure in the conference to reject the recommendations which incorporated in Poland towns and territories which were overwhelmingly German by language, race and inclination...” 14)

 

“France’s only real interest in Poland was to weaken Germany by giving the Poles areas to which they had no claim.” 15)
 

“Do examine the treaty and you will find that whole populations, against their will, were delivered into the power of those who hated them, while their economic resources were snatched away and handed over to others. The result of such directives has to be hatred and bitterness, if not despair. It may take years until these oppressed nations are able to shake off the yoke, but as sure as night follows day, the time will come when they will try to break free. We have a peace-treaty, but it will not bring lasting peace, as it was founded on the quicksand of selfishness.” 16)
 

Replies: @L.K

After the Versailles Treaty, German West Prussia was granted to Poland and the new Polish Corridor physically separated East Prussia from the rest of Germany. This was something Germany never accepted, except Weimar Germany was weak. This was the issue that the Hitler regime attempted to settle with Poland through negotiations.

Influential US Professor of diplomatic history, C. Tansill, wrote:

...In dealing with Danzig, they granted it to Poland because of economic considerations. They conveniently overlooked the fact that, from the viewpoint of population, Danzig was 97 per cent German. ...
To the Germans this large measure of Polish control over the city of Danzig was profoundly irritating, and at times the actions of the Polish authorities in connection with foreign relations and the establishment of export duties seemed unnecessarily provocative.
From the viewpoint of economics, Polish control over Danzig had the most serious implications. By altering the customs tariff Poland could seriously affect the trade of the port, and, through control of the railroads of the free city, the Polish government could extend important favors to the competing port of Gdingen.26 ...

... In 1938 and 1939 Hitler tried in vain to secure from the Polish government the right to construct a railroad and motor road across the Corridor. Relying upon British support, the Polish Foreign Office, in the spring of 1939, rejected any thought of granting these concessions. This action so deeply angered Hitler that he began to sound out the Soviet government with reference to a treaty that would mean the fourth partition of Poland. Polish diplomats had not learned the simple lesson that concessions may prevent a catastrophe.
 

That war declaration was 3. September 1939. Two days after the invasion. Their ultimatum may not have given two days, but Hitler had two days to see that Stalin does not attack at the same time with Germany.

But I accept your answer. I must find a stronger argument to support the claim that Hitler's main goal for the war was outrooting Jews in order to later move them to a new homeland in Palestine. There are other arguments for this claim, but an attack to Poland can be explained in a different way, like that Hitler was stupid and could not see into what war he takes Germany.

But what do you say about taking Japan as an ally? In the Protocols of the Elders of Zion there are mentioned only two countries controlled by the Elders (Jacob Schiff and others) so much that they can raise their arms against any country opposing the Elders. Japanese believed in the existence of the Elders when they got a loan for a war against Russia in 1904. The other country mentioned was the USA, and in 1917 the USA was brought to the WWI by Jewish bankers in exchange for a promise of a homeland in Palestine. That was true and Hitler knew it. So, he allied with Japan and the USA forced Japan to a war, Japan attacked the USA, both parties were off the main theatre for some time. Japan could not attack Soviets, and Sorge leaked the date of Barbarossa. Does this look to you as someone was arranging something?

Replies: @John V., @John V.

But France and England gave Hitler two days to withdraw. Why did Hitler not withdraw when he saw that Stalin did not attack, that is, assuming that Hitler did not want a world war but just a part of Poland? By not withdrawing he decided for a world war, must have understood that such a war would come, must have understood that Stalin is not reliable and that very possibly it would be a repetition of the situation in the first world war. Still he decided not to withdraw.

Replies: @Wally, @John V.

Not exactly. In 1914 the Russian Empire occupied the whole of Finland, Congress Poland, the Baltic Countries. In 1939 Russia re-occupied only parts of them. The extra-territory was Galitia and Bukovina.

Stalin wanted to recover Russian lost territories. Why was that worse than Hitler's desire to recover German territories? It seems that people cannot get over the meme of Russian innate malfeasance.

Replies: @john v.

"Hitler and Stalin were supposed to attack Poland at the same time. If that had happened, France and the Great Britain would have not declared war to Germany, and there would have been no World War 2."

That is an interesting theory. I know they were supposed to attack at the same time and Germans thought they would, but is there an reason to think that Germany would not have ended up with a war against France and England?

Hitler could not attack France in any other way than through Belgium, which would very probably bring in England even if England had not declared war the same time with France. Thus, if France would be at war with Germany, so would England.

Germany attacked Poland 1. September 1939, two weeks after signing the Molotov-Ribbentrop pact, France and England declared was 3. September and the SU attacked 17. September. But before the Molotov-Ribbentrop agreement France and England thought that Germany and the SU were sworn enemies and for that reason must have considered Soviets on their side, probably also negotiated with them. The relations between Poland and Germany deteriorated for a longer time. It seems to me that France and England intended to declare war on Germany in case it invades Poland already before the Ribbentrop-Molotov agreement. Thus, the claim would be that signing of this agreement would have scared France and England from following the policy they already had decided on. i rather doubt it. What I think would have happened is that when the Ribbentrop-Molotov agreement was signed, France and England immediately contacted Stalin and asked what does this mean, and they got an answer that made them to keep the original plan, and this agreement included that Stalin does not attack Poland at the same time as Germany. Had there not been such an agreement, France and England would have declared war on the SU soon after 17. September.

Replies: @john v.

"Why Hitler attacked Poland? Maybe he wanted to recover the lost German territories, or maybe Stalin convinced him somehow. "

Hitler attacked 1. September 1939. France and England put an ultimatum on Germany expiring 3.September 1939. Stalin had not attacked. If Hitler wanted to avoid the war, even if he was tricked by Stalin, he could announce withdrawal of German troops from Poland before the ultimatum expired. He did not do so, therefore he decided to start a world war. The attack to Poland must have been planned before the Ribbentrop-Molotov agreement, thus Hitler planned an attack and could not know if Stalin would join him. These things show that Hitler needed to attack Poland even if it meant a world war where Germany would very probably be in the same situation as in the first world war.

When Hitler took over Poland he started collecting Jews to camps. These Jews were finally not exterminated and nobody anymore claims that there was any extermination plan in 1939. The plan was also not to keep unreliable people in camps. Jews were to be moved and after the war they were to be moved to a new homeland. What can be this homeland? Some still claim it was Madagascar, but if so then why did Hitler make the Haavara agreement? Haavara was to take German Jews with their capital to build the initial infrastructure to new Israel in Palestine, not Madagascar or any other place. No other country, including the USA which was so controlled by bankers that it was taken to WWI in exchange of a promise of a homeland in Palestine, agreed to take Jews. So, they were moved by Hitler to wait for transfer to the new homeland.

I find impossible to explain these issues by Hitler's desire to get some land from Poland, or his worry of the situation of Germans in Poland. Jews are mentioned 445 times in Mein Kampf, Poles only 4 times (Finns and Swedes not at all). Jews were the central issue to him and he wanted to transform them out of Europe to a new homeland, not to exterminate all of them.

Replies: @John V.